Treating tungsten.



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I v Specification Letters ligatent. Application and July 2,1900, SerialIl'o. 324,392.

To all whom it may concern:

Be it known that I, AxnL O. Arrnnnnno, a subject of the King of Sweden,residing atSchenectady, county of Schenectady, State of New York, haveinvented certain new and useful Improvements in Treating Tungsten, ofwhich the following is a specification.

My present invention relates to a process of treating refractory metalsand materials,

whereby I- am able to build up refractory conductors for lamps,furnaces, and the like, and then machine orotherwise work the conductorsinto complex forms. As a suitable refractory material I may use one ofthe high melting metals of that class of. which tungsten is typical. I

In carrying out my invention I treat the refractory material in avacuum, and I so conduct the operation that at a certain stage I obtaina product which can be drilled, filed, planed and otherwise worked intocomplex forms such as tubes, cups, clamps,.hel]ices and the like.

The chemical reactions involved are probably of a complex nature, and itseems to 'me possible that various molecular changes occursimultaneously with the chemical changes, thus modifying the physicalproperties of the product, but whether this is true or not I havehereinafter described the steps of this method of treatment with suchdetail that a person skilled in the art will be able to reproduce theprocess and obtain the bene fits resulting therefrom. T p l Variousrefractory metals such as tungsten are ordinarily obtainedin the form ofa dark powder, the particles of which do not cohere and cannot be weldedtogether or agglomerated by methods applicable to low melting metals.Unless the material is subjected to some special treatment, solid con--ductors of complex form and good mechanical strength cannot be obtained.These difliculties are overcome by the process hereinafter described.

According to this process tungsten or other refractory powder is mixedwith a small quantity of glucose or other suitable binding material andis then squirted or pressed by heavy pressure into rods, bars, or otherbodies. A small quantity of tungstic oxid may be added to the mixture toserve as an oxidizing agent for carbon whether the latter is present asan impurity in the tungsten or comes from carbonization of the binder.

The quantity of tungstic oxid is preferably ust suflicient to remove allthe carbon.

Patented Dec. 1 2, 1911.

The squirted rods, produced as above described, are not strongmechanically, although they retain their shape and can be handledwithout difiiculty. They do not work well under a cutting tool and tendto crumble away and disintegrate when subjected tothe pressure of adrill, file or'similar'tool.

' According to the'next step in my operation, the squirted rod or baris-"he'ated'for an hour or two in'a vacuumto a temperature of' about1300 (3., whereby wonderful changes take place in the physicalcharacteristics of the material. It is greatly increased in strength andtenacity and be comes much like artificial graphite in its mechanicalproperties. I have mentioned the temperature of 1300 C. as being asuitable one for this treatment, but I find that the best temperaturedepends somewhat on the percentage of carbon present in the originalmixture; also on the percentage of tungstic oX-id added to the mixture,and on the intensity of the pressure to which the mixture is subjectedduring the squirting operation. An excess of carbon lowers this criticaltemperature 100 or so, while an excess of tungstic oxid raises theallowable temperature about the same amount. I also find that if thesquirting pressure, has been low the temperature suitable for obtainingthe desired result may be higher than that suitable when the pressurehas been exceedingly heavy. Although I do not wish to be limited to anyparticular theory, I think the difference in result produced by adifl'erence in pressure is due to the molecular distances in thematerial, or in other words, to the compactness of the material; aclosely packed body requiring less heat than a loosely packed one. i Thethird. step in my process consists in machining the refractory body intothe desired shape. This may be done by drilling, sawing, filing, etc.,the material being manipulated with the same ease as artificialgraphite;

The fourth and last step in my process 5' In general this last heattreatment should reach a temperatureabove 1600 C. Except as regardstemperature, this heat treatment need'not be substantially differentfrom the first. Its effect being produced through the action of heatupon the body, no special cooling or chilling is necessary in connectionwith it. u V

The ,final product may be made so hard that a file or drill will notwork it. I am thus enabled to obtain in the desired form, the mostcomplex structures that would probably ever be desired in electricfurnace work or in other arts where a highlyrefractory material isdesirable.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,-

1. The process which consists in forming a body consisting substantiallyof compressed refractory metal, heating said body to strengthen it andrender it machinable, the heating temperature being well below thefusing point of the metal, machining said body to a predetermined shape,and subsequently heating said body to render it hard and strong.

'2. The process which consists in compressing .tungsten powder into acompact body, heating the same in a vacuum at a temperature well belowits melting point to render it machinable, and subsequently heating to ahigher temperature to render it strong and refractory.

3. The process which consists in forming a compact body consistingsubstantially of finely divided tungsten, heating the same in a vacuumto a temperature of about 1300 C., whereby it is rendered strong andWorkable, and subsequently heating to a temperature above 1600 C. topurify the material and render it suitable for use as a refractoryconductor. 4 I

4. The process which consists in heating in a vacuum abody consistingsubstantially of finely divided tungsten to strengthen it, machiningsaid body to a re-determined shape, and subsequently heating the same toharden it. I

5. The process which consists in mixing tungsten with a binder and asmall quantity of oxid of tungsten pressing the mixture into a compactbody, heating said body to a temperature. of about 1300 degrees C. torender it strong and workable, machining said body into a redeterminedshape, and subsequently 'heatlng said bod to a temperature above 1600degrees to purify the material and render it suitable for use as arefractory conductor.

6. The process which consists in forming a compact body consistingsubstantially of finely divided refractory metal, heating said body to atemperature of about 1300 C. so as to render it machinable, machiningit,

and subsequently heating it to a higher temperature to harden it.

7. The process which consists in forming a compact bodyconsisting'substantially of refractory metal powder, heating said bodyto render it machinable, machining said body to,the shape desired, andthen heating said body to a higher temperature to render it strong.

In witness whereof, I have hereunto set my hand this 30th day of June,1906.

AXEL O. APPELBERG. Witnesses:

EnwAnnWmLIAi/ls, J r., ARBA B. MARVIN, Jr.

